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/*
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* Copyright (c) 2013, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package org.graalvm.compiler.phases.common;
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import org.graalvm.compiler.debug.DebugCloseable;
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import org.graalvm.compiler.debug.DebugContext;
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import org.graalvm.compiler.graph.Node;
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import org.graalvm.compiler.nodes.AbstractBeginNode;
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import org.graalvm.compiler.nodes.BeginNode;
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import org.graalvm.compiler.nodes.DeoptimizeNode;
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import org.graalvm.compiler.nodes.FixedWithNextNode;
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import org.graalvm.compiler.nodes.GuardNode;
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import org.graalvm.compiler.nodes.IfNode;
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import org.graalvm.compiler.nodes.StructuredGraph;
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import org.graalvm.compiler.nodes.StructuredGraph.GuardsStage;
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import org.graalvm.compiler.nodes.StructuredGraph.ScheduleResult;
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import org.graalvm.compiler.nodes.cfg.Block;
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import org.graalvm.compiler.phases.BasePhase;
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import org.graalvm.compiler.phases.graph.ScheduledNodeIterator;
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import org.graalvm.compiler.phases.schedule.SchedulePhase;
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import org.graalvm.compiler.phases.schedule.SchedulePhase.SchedulingStrategy;
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import org.graalvm.compiler.phases.tiers.MidTierContext;
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/**
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* This phase lowers {@link GuardNode GuardNodes} into corresponding control-flow structure and
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* {@link DeoptimizeNode DeoptimizeNodes}.
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*
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* This allow to enter the {@link GuardsStage#FIXED_DEOPTS FIXED_DEOPTS} stage of the graph where
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* all node that may cause deoptimization are fixed.
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* <p>
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* It first makes a schedule in order to know where the control flow should be placed. Then, for
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* each block, it applies two passes. The first one tries to replace null-check guards with implicit
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* null checks performed by access to the objects that need to be null checked. The second phase
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* does the actual control-flow expansion of the remaining {@link GuardNode GuardNodes}.
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*/
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public class GuardLoweringPhase extends BasePhase<MidTierContext> {
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private static class LowerGuards extends ScheduledNodeIterator {
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private boolean useGuardIdAsDebugId;
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LowerGuards(boolean useGuardIdAsDebugId) {
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this.useGuardIdAsDebugId = useGuardIdAsDebugId;
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}
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@Override
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protected void processNode(Node node) {
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if (node instanceof GuardNode) {
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GuardNode guard = (GuardNode) node;
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FixedWithNextNode lowered = guard.lowerGuard();
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if (lowered != null) {
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replaceCurrent(lowered);
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} else {
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lowerToIf(guard);
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}
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}
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}
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@SuppressWarnings("try")
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private void lowerToIf(GuardNode guard) {
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try (DebugCloseable position = guard.withNodeSourcePosition()) {
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StructuredGraph graph = guard.graph();
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AbstractBeginNode fastPath = graph.add(new BeginNode());
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fastPath.setNodeSourcePosition(guard.getNoDeoptSuccessorPosition());
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@SuppressWarnings("deprecation")
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int debugId = useGuardIdAsDebugId ? guard.getId() : DeoptimizeNode.DEFAULT_DEBUG_ID;
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DeoptimizeNode deopt = graph.add(new DeoptimizeNode(guard.getAction(), guard.getReason(), debugId, guard.getSpeculation(), null));
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AbstractBeginNode deoptBranch = BeginNode.begin(deopt);
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AbstractBeginNode trueSuccessor;
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AbstractBeginNode falseSuccessor;
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if (guard.isNegated()) {
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trueSuccessor = deoptBranch;
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falseSuccessor = fastPath;
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} else {
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trueSuccessor = fastPath;
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falseSuccessor = deoptBranch;
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}
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IfNode ifNode = graph.add(new IfNode(guard.getCondition(), trueSuccessor, falseSuccessor, trueSuccessor == fastPath ? 1 : 0));
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guard.replaceAndDelete(fastPath);
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insert(ifNode, fastPath);
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}
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}
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}
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@Override
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protected void run(StructuredGraph graph, MidTierContext context) {
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if (graph.getGuardsStage().allowsFloatingGuards()) {
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SchedulePhase schedulePhase = new SchedulePhase(SchedulingStrategy.EARLIEST_WITH_GUARD_ORDER);
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schedulePhase.apply(graph);
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ScheduleResult schedule = graph.getLastSchedule();
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for (Block block : schedule.getCFG().getBlocks()) {
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processBlock(block, schedule);
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}
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graph.setGuardsStage(GuardsStage.FIXED_DEOPTS);
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}
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assert assertNoGuardsLeft(graph);
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}
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private static boolean assertNoGuardsLeft(StructuredGraph graph) {
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assert graph.getNodes().filter(GuardNode.class).isEmpty();
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return true;
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}
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private static void processBlock(Block block, ScheduleResult schedule) {
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DebugContext debug = block.getBeginNode().getDebug();
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new LowerGuards(debug.isDumpEnabledForMethod() || debug.isLogEnabledForMethod()).processNodes(block, schedule);
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}
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}
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